cuts out until at higher speeds and engine warm, toxic fume light too????

I have a renault megane 03 plate, 1.6 petrol its been cutting out when starting up and needs extra revs to get it going, recently even the revs haven't kept it going and it just keeps cutting out when my foot comes off the gas a little until its up in higher speeds and warmed up. Then a day after this the toxic fume light and service light came on. I've read lots of forums about what it could be and people seem to have had the same problem but have ended up spending loads of different solutions and parts (suggested and carried out by renault garages) which have done nothing in the way of solving the problem. Any ideas on what could actually be the problem as i certainly do not have the funds to pay out £700-£1000 to the renault garage not to fix the problem. Also is it safe to drive with the toxic fume light on? (I haven't so far, but will be needed to soon, and certainly to at least drive it to the garage)
Thanks